Field of Invention
The present invention relates to a toric lens for visual correction.
Description of Related Art
A lens is an optical device for visual correction. Toric lenses are used for the correction of astigmatism. A stigmatism is an eye condition with blurred vision as its main symptom. The front surface of the eye (cornea) of a person with astigmatism is not curved properly. The curve is irregular, typically involving one half being steeper than the other. Sometimes one area is steeper than it should be. When light rays enter the eye, they do not focus correctly on the retina, resulting in a blurred image. Astigmatism may also be caused by an irregularly shaped lens, which is located behind the cornea.
Contact lenses for correcting astigmatism have been known in the market for at least since the 1980's. While there are toric lenses which serve their purpose well, the lens design are considered complicated. Worse yet, to fulfill patient's need for visual acuity, over 3000 stock keeping unit (sku) is required. This not only add burden to lens manufacturers for manufacturing and warehousing, but also a burden for whole sellers as well as eye care professional in keep big and complicated inventory. In addition, to cover visual correction needs, higher lens thickness is required. And this brings not only more difficulty in manufacturing, but also make lenses less comfortable and clinically less healthy for eye due to decrease of oxygen transmissibility.
Because of the above, there is a great need for smarter and novel lens design for correcting astigmatism which not only make lens manufacturer becomes able to simplify their manufacturing process, reduce the cost of inventory, but also make lenses more comfortable to wear and improve eye health.